South Korea said Tuesday that it will halt all Iranian oil imports from the start of July in response to a European Union insurance ban on tankers carrying crude from Iran.

The EU and United States have been widening sanctions against Iran recently to put pressure on Tehran to curtail its nuclear program.

Western powers say they believe the program is intended to build nuclear weapons, but Iran insists it is for peaceful purposes.

South Korea is the first major consumer of Iranian oil in Asia to suspend all imports. Iran's other big oil customers in the region are Japan, China and India -- none of which have announced plans to stop receiving shipments.

The South Korean Ministry of Knowledge Economy said in a statement Tuesday that it relies heavily on European companies for insurance of its oil imports and has sent representatives to the EU to make the case for continuing insurance coverage.

"The government has been putting contingency plans in place in case Iranian oil imports would be stopped," the statement said. Alternative supplies are being sourced from Qatar, the United Arab Emirates, Oman and Kuwait.

South Korea already lowered its Iranian oil imports by 40% between January and May to try to lessen its dependence on them, according to government figures.

There was no immediate reaction from Iran.